// 起始时间
// 1980年1月1日星期二
// 前面有两个空位
// 一年有 365天 366天
// 需要算出今年是 365 还是 366

var year = 2019;
var mounth = 5;
document.querySelector('#nian').innerHTML = year;
document.querySelector('#yue').innerHTML = mounth;


// 总天数

var days = 0;

// 判断是不是闰年
function runNian(y) {
	if (y % 400 === 0 || (y % 4 === 0 && y % 100 !== 0)) {
		return true;
	} else {
		return false;
	}
}
// 算1980到现在的头一年有多少天
for (var i = 1980; i < year; i++) {
	if (runNian(i)) {
		days += 366;
	} else {
		days += 365;
	}
}
// 今年一月到这个月的上个月多少天
for (var k = 1; k < mounth; k++) {
	switch (k) {
		case 1:
			days += 31;
			break;
		case 2:
			if (runNian(year)) {
				days += 29;
			} else {
				days += 28;
			}
			break;
		case 3:
			days += 31;
			break;
		case 4:
			days += 30;
			break;
		case 5:
			days += 31;
			break;
		case 6:
			days += 30;
			break;
		case 7:
			days += 31;
			break;
		case 8:
			days += 31;
			break;
		case 9:
			days += 30;
			break;
		case 10:
			days += 31;
			break;
		case 11:
			days += 30;
			break;
		case 12:
			days += 31;
			break;

	}
}
// 算ben一共多少天
var day = 0;
switch (mounth) {
	case 1:
		day += 31;
		break;
	case 2:
		if (runNian(year)) {
			day += 29;
		} else {
			day += 28;
		}
		break;
	case 3:
		day += 31;
		break;
	case 4:
		day += 30;
		break;
	case 5:
		day += 31;
		break;
	case 6:
		day += 30;
		break;
	case 7:
		day += 31;
		break;
	case 8:
		day += 31;
		break;
	case 9:
		day += 30;
		break;
	case 10:
		day += 31;
		break;
	case 11:
		day += 30;
		break;
	case 12:
		day += 31;
		break;

}
// 算上个月多少天
var prevDay = 0;
switch (mounth - 1) {
	case 1:
		prevDay += 31;
		break;
	case 2:
		if (runNian(year)) {
			prevDay += 29;
		} else {
			prevDay += 28;
		}
		break;
	case 3:
		prevDay += 31;
		break;
	case 4:
		prevDay += 30;
		break;
	case 5:
		prevDay += 31;
		break;
	case 6:
		prevDay += 30;
		break;
	case 7:
		prevDay += 31;
		break;
	case 8:
		prevDay += 31;
		break;
	case 9:
		prevDay += 30;
		break;
	case 10:
		prevDay += 31;
		break;
	case 11:
		prevDay += 30;
		break;
	case 12:
		prevDay += 31;
		break;
}
console.log(prevDay);

// 因为总天数是从星期二开始的,想从星期日开始算
days += 2;
// 算本月1号是星期几
var start = days % 7;
// 算当前页面的日历能多少数字
var num = 42;

// 日历开头空几个
// 本月多少天
// 下个月多少天
var nextDays = num - start - day;
// 取到今天是几号
var thisdate = new Date().getDate();

var date1 = document.querySelector("#date1");
console.log(date1);
for (var j = prevDay - start + 1; j <= prevDay; j++) {
	date1.innerHTML += "<span class='c'>" + j + "</span>";
}
for (var a = 1; a <= day; a++) {
	if (a == thisdate) {
		date1.innerHTML += "<span class='b'>" + a + "</span>";
	} else {
		date1.innerHTML += "<span>" + a + "</span>";
	}
}
for (var s = 1; s <= nextDays; s++) {
	date1.innerHTML += "<span class='c'>" + 	 s + "</span>";
}
//
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